The invention is applicable, for example, to a telecommunication system using optical data transmission technology. One specific example of using this invention is in a long-haul dense wavelength division multiplexing (DWDM) transmission system, such as the hiT 7300 Optical Packet Transport platform of Coriant GmbH & Co. KG, DE. This platform is optimized for high-capacity transport of data in optical long-haul networks, at bit rates from 2.5 Gbit/s to 100 Gbit/s per wavelength and further is designed to be upgraded for 400 Gbit/s and more in the future. The key building blocks of this system include optical amplifiers, routers, optical add-drop multiplexers (OADMs), reconfigurable optical add-drop multiplexers (ROADMs), photonic cross-connects (PXCs) and additional function units, such as “hot-pluggable” transponders and multiplex transponders, with tunable XFPs (small form-factor pluggable transceivers), SFPs (10 Gbit/s small form-factor pluggable transceivers) and CFPs (100 Gbit/s form-factor pluggable transceivers) that enable easy configuration.
These and other functional units usually are provided as plug-in units to be assembled in sub-racks or shelves in a rack of a telecommunication system, such as an optical DWDM system, and may be configured according to customer demand.
Within each shelf, power supply of and communication between the plug-in units is usually performed via a so-called backplane, said backplane also connecting the plug-in units with a control board/unit usually also provided within each shelf.
U.S. Pat. No. 6,822,874 B1 and WO 2005/051006 A1 describe examples of modular telecommunication platforms using plug-in units. U.S. 2008/0304428 A1 and EP 2051453 A1 describe optical transmission networks which also are examples of systems to which the invention can be applied. Any of the network elements described therein provide examples of the plug-in units addressed above. The hiT 7300 platform of Coriant is further described in publications of Coriant and its predecessor, Nokia Siemens Networks, such as at www.coriant.com/products/hiT7300.asp. Of course, the invention is not limited to any particular platform, but can be used for any type of telecommunication system and, more specifically, optical DWDM systems.
In these kinds of systems, for particular applications or for purposes of upgrading, it may be desirable to combine two or more plug-in units into a specific package or cluster. A cluster is formed, for example, if more than one printed wiring board (PWB) is needed for one functional unit with more than one interface to the backplane. When combining several PWBs into one functional unit, dedicated connections between the PWBs are needed. In particular when clusters are formed for upgrading a telecommunication system, the preinstalled backplane often will not support the necessary dedicated connections. In the past, this issue has been addressed either by redesigning the backplane to provide the necessary connections, by configuring the printed wiring boards in such a way that a number of different printed wiring boards are combined and connected directly using board-to-board connectors to form multi-PWB plug-in module, or by combining several printed wiring boards to form a cluster using more than one backplane connection. Those clusters might form one mechanical unit, but they might also be composed of separate mechanical entities.
If different combinations of different printed wiring boards (forming different clusters) are to be connected via dedicated connections within the backplane, the amount of possible combinations is limited and the backplane costs will be increased. There is little flexibility. If additional, not predesigned combinations of PWBs shall be added later, e.g. for upgrading the telecommunication systems, a redesign of the backplane will be necessary. This leads to additional costs and interferes with backwards compatibility concerning already installed bases at a customer's site.
Combining several PWBs into clusters, forming specialized plug-in units will make the number of different individual clusters will be very high because different numbers and combinations of different PWBs will be configured as clusters. The large amount of different predesigned clusters results in higher logistic costs at manufacturing. Moreover, the weight of one cluster, which is the sum of the individual PWBs combined, will increase, making the cluster more difficult to handle. Additionally, by combining several PWBs into one cluster, it may be expected that the mean time between failures (MDPF) will decrease.
The invention provides an optical DWDM system which allows easier and more flexible modification and upgrade of the system configuration.